I think having two different actresses playing Mystique will be difficult to ignore since she's not supposed to age a lot. Fassbender aging into McKellan is a little easier to imagine, but I'm already having issues in my head between McAvoy and Stewart...

I mean there is heavy make-up on Mystique, but it'll still be weird.

How is it hard for you to imagine a shape-shifter looking different? I think it's probably the easiest to accept!